4.27.2009

(Bloomberg) -- The demise of the dinosaurs probably occurred 300,000 years after a giant meteor struck what is now Mexico, scientists said, casting doubt on a popular theory that the impact triggered a mass extinction.

The Chicxulub crater, which is about 180 kilometers (112 miles) across, was formed on the Yucatan peninsula when an extra-terrestrial object struck Earth 65 million years ago. Since its discovery in 1978, the crater has been cited as evidence that the impact’s aftermath led to the extinction of about 65 percent of all species including the dinosaurs.

New clues at other sites in Mexico showed that the extinction must have occurred 300,000 years after the Chicxulub impact and that even larger asteroids may not be the purveyors of doom they’re thought to be, according to a paper published in the Journal of the Geological Society by researchers from Princeton, New Jersey, and Lausanne, Switzerland.

“We found that not a single species went extinct as a result of the Chicxulub impact,” said Gerta Keller, a professor of geosciences at Princeton University, in a release distributed by the Geological Society of London. “These are astonishing results.”

Keller and Thierry Adatte from the University of Lausanne found sediments linked to the mass extinction that were deposited above the sediments from the time of the asteroid impact. Proponents of the Chicxulub impact theory explain this discrepancy in the sedimentary record with earthquakes and tsunamis resulting from the asteroid impact.